If it's your name, then it's your name. You've clearly fallen in love with the name and you believe it's the right name for you; your family will need to learn to respect your decision. You should never have to resent your own name: many cis people who resent or dislike their birth names wind up changing them when they're adults, so you're perfectly entitled to live with a name that feels comfortable to you. As a compromise, would you consider allowing your family to pick out your second name? You do, of course, have veto power.
Whenever I hear someone complain that a name is juvenile or unprofessional, I'm reminded of one of my favourite celebrity doctors: Dr Pixie McKenna. Her birth name is Bernadette, but she prefers to be known as Pixie, which is (I believe) a nickname. She's carved out a successful career as a doctor, television presenter and columnist. She's an expert in sexual health, dermatology, women's health and health promotion, and she has a private practice in London's prestigious Harley Street. All this whilst being known as 'Dr Pixie'. She's doing just fine in a professional setting, I can assure you. And in this multiracial, multicultural world, no name belongs to any particular race; we can name ourselves anything we wish.
